Diagnosis of Posttraumatic Stress Disorder (PTSD) has been focused on phenomenological indicators such as reports of panic attacks, nightmares, disability in functioning, and other measures that focus on symptomology. To applicants' knowledge, no metabolic or physiological changes in the molecules present in biological fluids or tissues of the subject have been employed for this purpose. The present invention has identified markers that circulate in biological fluids of a subject afflicted with PTSD that change in concentration or level in comparison to subjects that are not afflicted with this disorder.